FIG. 1 shows by way of example a common slide fastener which has hitherto been employed for joining and separating the edges of sheets.
The fastener comprises a pair of strips 1 of a knit fabric, interlocking members 3 of metal or plastic attached to each strip 1, and a slider 5 for interlocking the interlocking members 3 on one strip 1 with those on the other, each strip 1 being attached to the edge of one of two sheets 7.
The fastener as hereinabove described has, however, not been capable of forming a seal between the joined edges of the interlocking members, but it has usually been necessary to provide the joined edges with a waterproof cloth, or sealing member to form a seal therebetween (see e.g. patent application laid open under No. Sho 60-198102 and Utility Model Application laid open under No. Sho 63-160469).
It has, therefore, been proposed in the above applications that the interlocking members be coated with a viscous resin, or given water-repelling treatment to be capable of forming a seal therebetween. These proposals, however, call for extra work or treatment. Moreover, in some cases of fastener application, as in a boot for which grease is used, it is likely that the lowering in quality of the materials employed for such treatment may result in a lower sealing property with the passage of time.
To overcome the above problems, the applicant of the present application has proposed a seal fastener as shown in FIGS. 2 and 3, and as described below (see patent application laid open under No. Hei 1-204607) whose disclosure is hereby incorporated by reference herein.
It is provided between the edges of sheets 7 for joining or separating them, and comprises a male interlocking strip 13 formed along one of those edges and having a bulging edge 14, a female interlocking strip 16 formed from a rubbery elastic material along the other edge and having an interlocking groove 17 for receiving the male interlocking strip 13 therein, and a clamping insert 19 formed from a spring material and embedded in the female interlocking strip 16 about its interlocking groove 17 for imparting a resiliently clamping force to the female interlocking strip 16 between the facing edges of its groove opening.
The problems which will be pointed out below have, however, been found to arise in connection with the use of the seal fastener as hereinabove described:
(1) It is not always easy to interlock the male interlocking strip 13 with the female interlocking strip 16; and
(2) The fastener is not necessarily good in durability, since its repeated use results in the formation of a crack behind the bulging edge 14 of its male interlocking strip 13, or the lowering of the resiliently clamping force of its female interlocking strip 16.
Under these circumstances, it is an object of this invention to provide a seal fastener which is easy to interlock and is good in durability.